This invention relates to a method of lubricating a rock drill and it also relates to a rock drilling apparatus.
Conventionally, for lubricating a rock drill that has a compressed air operated impact motor, oil is supplied to the compressed air supply conduit at a distance from the rock drill and transported to the rock drill by the air. In this way, the sliding surfaces between the hammer piston and the cylinder of the impact motor are lubricated. Usually a small part of the supplied air leaks forwardly in the rock drill and lubricates the piston stem and a rotation chuck. If the rock drill has a piston stem actuated ratchet mechanism for rotating the chuck, the leaking oil is also used to lubricate this mechanism. With this method, more oil must normally be added to the drive air than would be necessary for lubricating the piston and cylinder in order to ensure proper lubrication of the other parts to be lubricated.
Another method is described in U.S. Pat. No. 3,983,788. In the impact motor illustrated therein, the hammer piston is not guided against the cylinder but its two piston rods are guided in guide bushings whereas there is a clearance between the hammer piston and the cylinder. Therefore, no oil need to be added to the drive air for the impact motor, but there is a secondary compressed air supply hose for oil-loaded compressed air that is conveyed through passages in the housing to the guide bushings for the hammer piston.
It is an object of the invention to make it possible to adapt the lubrication to the various needs of the parts to be lubricated without making the rock drill or the lubricator complicated and without using additional hoses.